Receiver



April 26, 1938. M. G. CROSBY RECEIVER Filed Jan. 2l, 1955 2 Sheets-Sheet l INVENTOR MURRAY e. CROSBY` BY KZ ATTORNEY April 26, 1938. M G. CROSBY 2,115,360

RECEIVER Filed Jan. 2l, 1955 2 Sheets-Sheet 2 111111 lvvvvv Patented Apr. 26, 1938 UNITED STATES PATENT OFFICE RECEIVER.

Murray G. Crosby, Riverhead, N. Y., assigner to Radio Corporation of America, a corporation of Delaware Application January 21, ,1935, Serial No. 2,639

24 Claims.

sensitive to the reception of said waves irrespective of the nature of the modulation thereon and irrespective of the fact that the nature of the modulation on said waves may change in character from time to time due to causes encountered during the transmission of said signals.

More in particular this invention relates to a type of receiver wherein an automatic correction is produced to compensate for the type of multipath transmission fading distortion in which the signal modulation is distorted from an amplitude modulated wave to a phase modulated wave, or vice versa.

In my novel receiver a modulated wave is detected by twodemodulators, one of which is primarily responsive to phase modulated Waves and the other to waves modulatedin amplitude. A differential' voltage is produced by means described more in detail hereinafter in the outputs of the two demodulators and is utilized to actuate a phase shifting device which adjusts the phase of the filtered carrier utilized for demodulating purposes so that the audio detectors which render the signal for recording purposes are receptive to the type of modulation coming in at the particular time.

In an alternative arrangement, the differential voltage operates a switching device which switches the receiver output used for signal purposes from a phase modulation detector to an amplitude modulation detector.

In Crosby U. S. appln. Ser. No. 719,643, led April 9, 1934, Patent #2,019,446 dated October 29, 1935, I have disclosed a receiver which resembles the present receiver to the extent that in said receiver of said prior application the demodulator is caused to respond to the particular type of modulation predominant on the received Wave. For example, if a phase modulated wave has been distorted so that it has the semblance of an amplitude modulated wave, the receiver of the prior disclosure will amplify and demodulate the wave and render the signals. Conversely, if an amplitude modulated Wave has been transmitted and has been distorted during transmission so that it takes the character of a phase modulated Wave, said receiver will'receive, amplify, demodulate and record the same. by switching or reversing the nature of the demodulator at a rapid rate.

The receiver of the present invention has the advantage that it is capable of automatically This is accomplished Y (C'l. Z50-20) choosing the condition of reception which is i.

best at all times and automatically adapts itself to such reception. In the receiver of Crosby,v appln. Ser. No. 719,643, Patent #2,019,446, there might be a case where the modulation would re- 5 main undistorted for long intervals during which the switching device of said prior receiver Would be operated unnecessarily. Consequently, the said switching device might impair the signal to noise ratio. To illustrate this point, let the following example be taken. If the signal were being received as pure amplitude modulation and the switching device were in operation, the amplitude modulation signal and noise would be present one half of the time, so that their output would be halved. The other half of the time, the phase modulation noise would also be present. Thus, the receiver output might consist of one unit of signal as compared to two units of noise. In the receiver of the present invention, I when pure amplitude` modulation is received, the automatic adjustment makes the receiver receptive only to amplitude modulation, so that one unit of signal and one unit of amplitude modulation noise only is present. Consequently, an improvement of two to one in the signal noise ratio is eiected in the present receiver, as compared to receivers known heretofore. The same is true where the wave received is modulated in phase only.

IThe novel features of my invention have been pointed out with particularity inthe claims-'appended hereto.

The nature of my invention and the manner in which the same is Icarried out will beV under- 13 stood fromV the following detailed description thereof and therefrom, when read in connection with the attachedY drawings throughout which like reference numerals indicate like parts in so far as possible, and in which: I

Figure 1 illustrates a receiver including signal amplifying means, a detector from which the amplified signal may be obtained, and a pair of differential detectors which control the connection between the detector from which the signal is obtained and the receiver in a manner that is Vprimarily responsive to that type of modulai utilized in illustrating the operation ofthere- I ceivers in .theV prior gures.

YThe general operation of pointed outbrieflyY firstjin connection with the drawings. Reference will' be made YtotheV receiver oflig,Y 1 whichv shows Va specicembodi-KV ment in which a switch S' atrthe input ofthe Y Vaudio'jamplifier 24 V'fronti YWhich the signal ffor y .recording purposes is obtained is automatically connected Y'to/the output of transformer I6 the inputof which is connected in push-pull relation to the anodes of a pair of differentially connected detectors when the received Wave is modulated inphase either intentionally or in a manner to` simulate phasemodulationV due to distortion during transmission. YWhen the Wave received is amplitudefmodulation., .or simulates amplitude modulation due todistortion, the. said detector. from which'the signalfor recording purposes is. .Y

obtainedV is connected'ina manner described'later, .by the'swit'ch tethesecondaiiy'winding,of transn fformer'l, the 'primary'iwinding of which is connected: parallel vvith' the anodes and cathodes of said differentially connected detect'orsQIn ,thisjmannen the amplifierl from which the re- .corded energy: is obtainedjis caused to; respondto that type ofrmodulation; which is strongest.V Y Y Morcin detail', thasignal coming, in` on the antenna Yl Yis vfed to a superheterodyne; receiver consistingof aradi'o frequency"amplifier and demdulator'', aV highirequency oscillator'3 andan rintermediate frequency* amplifier s 4i.. 'llfhe high frequency oscillator 3 Jisiof theY aut'omaticjfrequenvcy controll'edi.type;A whose: frequency is partially dependent'upori tuning'` of the circuits thereof and partially dependent. upon the naturelof Ythe energy Y Vsupplied thereto. by .Wlay of'the automaticfre- Aquericy controlledA energy' supply line 21 VEnergy 'from the voutputt'of the intermediate frequency ,amplifier 4% isVA suppliedY toa unit 5:,1 including ak carrier filter circuit preferably'.offthecrystal type, an amplitude limiterorI automatici volume conf' trol, and where desiredgaphafse shifter.

Y .The filtered limited'.energyfis'.:fed` from the VV`former ii;Y the's'econdary Windingf of. Whih con-Y nects thecontrol gridsgfo'fr thediiferential detector tubes'8fm and' H in.. push-pull rela-tion, soV that stripped or filteredcarrierV energyis'appled-.from 5in phase Vopposition to the Vcontrol grids of 8. and 9j Vasl hasbeen illiistrated in. Eig. V3i by' vectors= E1 andrEi; At the same time, v'unfiltered carrier energy is supplied from lthe output: ofY the interr-VV Y resultant`V voltages are represented by the vectors .'lilayaiid"'E4` when the intermediate frequency ob;- `tained' by 'beating oscillations. from: 3; With'the re,-

ceived'wave, is; at the pea-k of the Yfilter in 5.1 YIfV the frequencyA of the oscillator'3 orn receivedsignal f yshould change', the; vectors of Fig.' v3' may shift tofthephase: change of Ei land; E25' 'asf effected: by'v the crystal filter.V Novv, theresultant voltages E3! and-Ei"areno'longeriequal. "Diferentialcurrents are developed: through. resistancesxlfll and IIfand 'these currents .produce voltagesfvvhichy actl through theltime constant unit l2 and modulator. M toY n Vshift'the frequency developed byl3 in theA direc- 1 75Y tion'necessaryto put the beatiV frequency back.' to

my device will be' the resonance frequency of the filter circuit in 5 andthe frequency of the intermediate frequency amplier 4. The time constant of the line Y21a` condenser and resistance l2 and modulator M 'input is such that it responds tofrequency changes but not to signal modulations. A change'of frequency in the opposite direction acts in a sense oppositely tothat indicated inFig. 4. Y The modu-V f latorM may include a therrnionic modulator tubeY having its input connected by resistance and capacity to the control circuit 21, and its anode coupled to a yreactance L in turn'coupled toJthe reactance L in a circuit of the thermionic gener.-V atorof the unit 3. The reactance L determines Qin part the frequency of .theV oscillations gener-` ated bythe oscillator in 3. -The condenser inthe time unit l2 also serves the purpose of keeping the audio'voltages from reaching* the high fre-'f quency roscillator .circuits in 3. In Y setting 'forth the operation of the frequency control circuits the modulatingflpotentials mayV be and haveY beendis- Y regarded.y V'I'he device operates as indicated on a r` changez of frequency Virrespective of the type 'of modulationV ion Vthe Wave and .irrespective of Whether the change-resulted from a change in the Wave.

l Y The'frequency control device; andinvparticular Y e the differential detectorsvlK and @nandrth'etime constantdevice !2 andV modulator M 'have been 'describedrindetailz and claimed in Crosby U. S.

application, Ser.V No. 616,803, 'iledf'JuneY 13, 1'932 Patent Vv$192,065,565: dated'December 29, 1936..

As, describedI in Crosby U; S. application ii-616,5V 803, Patent #2,065,565 .datedDecember 29; 193B,

25 f oscillationsl from 3 or Yorfga change in the received Y when the unfilteredV energyfrom 5 is applied cof -phasally tothe control grids of the,` tubes inthe vdifferential' detectors, andv the' unfilteredY energy is Vapplied Ain phase quadrature (90 orA 270) Vthe 'energy so' combined may be detected to produce',k

an output characteristic of'.A phase'modulations on 'i Y theun-lteredcarrier when the detector outputs are added differentially by the push-pull connec- 'y tion. '.TheY same arrangement Will .giveV output energy which varies inV amplitudein accordance withv amplitudey modulations on the' unfiltered carrier etc., Whenv the detector outputslare added f in parallelyby connecting-,the outputs in parallel.

This is because the output'of' bothltubes adds cumulativelyginthe output circuit; sothat the quency. s *Y `outputenergy waxes and rwanes'kv at' signalffre- The "ma-nner iniwhich my `receiver responds y' either to phase or amplitude modulation will now. Y

be: described.V In describing this operation irefn Y erence Will be made to'E'igs. 3, 4 and 5. 1 p Referring Vto Fig'. 3, Ei and Ezrepresent the Y. i VVltered carrier4 voltage fed to detectors Sand 9 via differential transformer 5'. .1 Es representsthe Y signa-levoltage"fedivia'transfcrmer l.. Thesevo'lt-*.6-l j Vages'combine'to--form resultant Els-,tonne detector Y tubfeandrresultantEli tothe other'l detector tub'e The 9,0. deg-ree phase relationship` betWeenEsV and of the phase shifter in unit 5. relation is maintained, except for the Vsudden phase deviations-dueto phase modulation,r in this position byv meansoii the automatictuning con`` i. if... Vtrol* which; inv turn, holds'thef intermediate `fre'V`V 1 quency .in-'tunewth the carrier lter.

,When phase modulationiis'applied, Es shiftsin i phasetoi'th'e positionfEsfin Figgfi. The filteredf .CaTYeIVOlgCS E1 andA Ezfdo-fnot shift'inphase* since thecarrier filter` removes the side-bandes# Y 'due'. to modulation anjdt consequently the4 phase'-4V Vthe voltages; Erf and Eris produced bym'eans i This 90l degree :6.5

shift due to modulation. The resultant voltages fed to the detector grids are E3 and E4 which are decreased and increased in amplitude, respectively. Es also shifts with modulation in the opposite direction to that shown in Fig. 4. Hence, the resultants E3' and E4 are increased and decreased, respectively. In this manner the phase deviations with modulation (which are fast enough so that time constant circuit I2 does not allow the automatic tuning control to correct for them) produce amplitude modulations onV the resultants. The envelopes of these amplitude modulations are 180 degrees apart in phase so that after detection the push-pull transformer I6 adds them in-phasev in the coupling tube outputs.

When amplitude modulation is applied to the signal voltage, Es, the amplitudes of the resultants E3 and E4 are modulated also. The envelopes of the amplitude modulations will be inphase so that the parallel connection transformer I5 will give the output.

The automatic tuning circuit functions in a manner similar .to the detection of phase modulation but due to the time constant circuit I2, only slow changes of phase furnish controlling energy. The normal phase relation (or mean phase relation when phase modulation is applied) of the detector grid voltages is as shown in Fig. 3. When the frequency of the energyfed to .the carrier filter, unit 5, varies, due to the extreme selectivity of the carrier filter, the phase of the output-changes. The detector grid voltages are then as shown in Fig. 5. The ltered carrier has shifted in phase and the resultants E3 and E4 are no longer balanced with respect to amplitude. With the detector grid voltages unbalanced, their plate currents will be unbalanced and there will be a differential voltage across resistors I3 and i I. This dilerential voltage is fed via line 21 and the time constant circuit I2 to the grid of modulator tube M. A variation in the grid voltage of modulator M causes a variation in its plate impedance. The modulators plate impedance is coupled to the high frequency oscillator tuning by means of a capacitive, inductive, resistive, or network coupling such as a transmission line or wave iilter. Hence, a variation of the modulator' plate impedance causes a variation in the tuning of the high frequency oscillator. By virtue of the controlling action of the voltage on the grid of the modulator, the variation of the high frequency oscillator tuning is held to a value just suiiicient to restore'the detectors to the balanced condition as portrayed in Fig. 3. When this balanced condition is obtained, the intermediate frequency energy is properly tuned through the carrier lter.

In order to combine the detector outputs in the two manners described above, the differential potentials produced by the diierential currents in Ill and il are impressed as shown on the control grids of a pair of differential coupling tubes I3 and I4. The anode electrodes of tubes I3 and I4 are connected as shown in push-pull or diferential relation, by way of the primary winding of transformer I6. The anode electrodes of tubes I3 and Ill are also connected in parallel as shown by way ofthe primary winding of transformer I5. Y

If the signal is coming in as a true amplitude modulation, or as a simulated amplitude modulation, energy varying at signal frequency willy appear in the primary Winding of I5 and be induced in the secondary Winding of I5. If the signal is coming in as true phase modulation, 0r simulated phase modulation, energy characteristic of the phase modulations on .the signal will appear in the primary winding of the transformer I6 and will be induced in the secondary winding of transformer I. Thus, if the outputs of these two transformers are detected as they are by demo-dulators Il and I8, the difierentialvcurrents across I9 and 20 may be utilized to loperate a polarized relay 23, including a switch Sito connect the receiver output including the tube 24,

transformer 25 and telephone or other indicator jack 26 to the output of i3 and I4, either by way ofthe transformer I5 or by way of the transformer I6, dependent upon whether the amplitude modulations or the phase modulations on the unfiltered carrier predominate.

Resistors ill and 22 match the impedance of the relay to the impedance of the detector outputs. Polarized relay 23 has its armature connected to the input of the receiver output coupling tube 24. The two contacts of the relay are connected .to the high ,sides of the secondary windings of the transformers I5 and I6 so that when the armature is in one position the receiver output .is connected to the amplitude modulation output transformer I5 and when the armature is in the other position, the receiver output is derived from the phase modulation transformer I Il. Consequently, if an amplitude modulated signal is distorted during transmission so that it resembles a phase modulated wave predominantly, .the relay will Vconnect the tube 2d to the transformer i8, whereas if an amplitude modulated wave resulting from amplitude modulation or distorted phase modulationis received, the tube 24 will be connected to the output of transformer I5.

The receiver of Fig. 2 is identical with the re.-

ceiver of Fig. 1 up to and including the detectors Il and I8 and the resistors IS and 2B. Moreover, the numbered parts up to and Vincluding the parts referred to of the two circuits correspond. In Fig. 2, however, the diiferentialvoltage from detectors I'.' and I3 is utilized to operate a phase adjuster which automatically keeps the phaseof the filtered carrier at the proper adjustment to receive that type of modulation which appears to predominate. The differential voltage from detectors Il and I8 is fed by way of time constant circuit 28, 23, in phase opposite to the screen grids of the modulator tubes 3i and 32 which, as shown, are connected in a differential phase modulation circuit including the elements Si, 3l, 32 and 33. The control grids of tubes 3| and 32 are connected as shown by way of a phase adjuster 33 to the output of the carrier lter and amplitude limiter 5. The phase adjuster 35 is so set that the filter synchronized carrier .wave reaches the control grids of the tubes 3l and 32 to excite the same in phase quadrature, or in 90 phase shifted relation.' As indicated above, when thevoltage on the screen grid of tube 3l goes down, the voltage on the screen grid of tube 32 goes up, and vice versa, since these tubes are connected as shown in push-pull relation to the tubes Ill and i3. When the voltage on the screen grid of one tube goes down, that tube, for example 3I, becomes inoperative and allows theA other modulator tube, for example- 32, tofurnish the carrier energy to theci'reuit 33. The phase of the carrier energy in 33 will accordingly'be determined, in part at least, by the phase of the carrier supplied to the control grid of 32. When 32 becomes inoperative, 3l supplies energy to the tubes 3| and 312.? Amodulator of the type just` described has been.Y described in detail and` claimed'in yCrosby application No'.V 690,330, led Sept. 21st, 1933, and CrosbyA applicationNo. 5881;

v 309;. ledjJan..23, 1932, Patent'No. 2,018,577, Y

'dated' May 25,.-1937; v V'The carrier energy from the modulator 3L 32iisY passed' through a. phase adjuster 34. to' the primarywinding of` a transformer 3e` and from the secondary Vwinding-of: transformer 35 to the control grids of tubes 3l: and 38. Since the secondary windingjofltransformer 35 connects the control grids of tubes 3T and 38 in push-.pull relation,` the carrier Yenergy from 34l is supplied to saidcontrol gridsxin phaseopposition. The suppressor'gridsoftubes 3l and'38 are connected in Vparallelv with the secondary winding of a transformer 3K6., which is in'turn connected with the Y 'Y matic switching or phase adjusting, as disclosed Vin this application. For instance, the. receiver-r output 'of the intermediate `frequency amplifier 4. The transformer 36 accordingly impresses unf ltered and'runlimited carrier energyV in phase on Kthe suppressor grids of tubes 3landj38. Tliedemodulated signal appearing across the resistors 39 and 40Ais`passcd from. said resistors tothe cou.- plingtubes 4I andf42r andthence to an indicator insertedat.V 4,4.v

Phase adjuster 34 may be adjusted to give optimum output of the audiok detectors k31V and 38.

jlThis adjustmentjis'. such "t'hat'rwhenfthe mod- 35.

" be maximum.. `Thus ii the modulation is pureV Vulation isy purely one Ykind','the audio output will amplitude` modulation the transformer I5V having .its primary winding connected in parallel with the anodesof tubes I3 and-I4, Willfurnish. the

output energy.V The differential. transformern I6 ,will furnish no energy. The secondaryywinding of transformery I5 supplies" energy tofthe input electrodes of tube I'I to thereby render. tube Il' Y more conductive and .cause more current to flow through resistor I9.Y V'I'his in turnflowers the volt- `age appliedto the screenv grid electrode of phase 'circuit 33. AssumedV thatgthe' phase ofthe car-Y rier'voltagerfed to the grid ofthe tuber32 is: 0,

modulator tube 3 I, so that it becomes'inoperative orrlessfoperative than the phaseV modulator tube Tube 32' accordingly supplies the energy to sincetube 32 is operative,`the phase of the voltenergy supplied byY way Yofv 36V tothe suppressor Y carrier are producedin the transformer 43.

With the above adjustments and circuit .con`

Ygrids of tubes 3-and 38. Signals characteristicf of .the amplitude modulations'on `the received Y stants left the same, if the modulation on Vthe carrierV changes .to phase modulation, the following Ycircuit operation takesplace. The differential transformer I6 will now'be energized; While,V the'trans'former I5 will. not be energized. Con-i sequently, tube Ihas its control grid biased less j negative'andincreased current flows in the anode circuit fof tube I8' and through the Yresistance 20. This increase of. current 'Y through *resistance 20 lowers the potential Vapplied to the screen grid of Y y tube `32,.and causes the Vsaine to become inoperative, or atleastless. operativethan tube 3|.

2,1115, aco

Hence, since the phase of the carrier voltage Von Y the grid; of tube 3l isi 90 romthat on Ythe tube 32, the phase of the voltage in the circuitr33 will be 90, instead of 0. Thus,;the carrier has. been shifted in phase 90 with. respect tothe unltered s'ignal'inY 36 in. the presence ofphase modulations. Yon thefcarrier waveaso that audio detectorsj3-1.

and 38 are now receptive to the said phase modu- Y .lations on the received carrier.

In; the circuit lofFig. 1, .the mechanical relay `23' may be replaced by any system of electron tubes or gaseous discharge devices, such as thyratron and neon tubes, to effect the less mechani-- cal switching action between the output of'. the receiver and the tube24;

that the relay23 switches the phase of the'carrier or. signal between the two proper adjustments, e.. g. 0 and 90, to

lation; Y

All of the'diierent circuits of my copending U.

receive the two typesof! moda/ S. application #719,643 Patent #2,019,446 dated l October 29, 1935,V may be utilized for Vthe-'auto- Y 'n of Fig. 4 of copendingfapplication, S. N.`f719,643 Y vPatent #2,019,446; dated October 29, 1935, may

be'arranged sothat the coupled'tubes 42 and 43 of said gure may be switched automaticallyY ,Y .3u

accordingly as the signal 'phaseV from'one type of modulation to theV other. Y

The circuits of FigsflV and 2 have been given Yfor'purposes of illustration. only, and-obviously many elements therein maybe altered Vor sub- `stituted without departing from thespirit of the present invention. yFor example, any tube shown therein may be replaced'byV tubes of other types, so long as saidv tubes used for replacement have the necessaryV elements to serve the purposes in hand. Moreover, although ,I have shown several sources of potential, it. will be realized .that theA f said, sources may be replaced by asingle source.

I claim;Y n l. In combination, a'system-for dernodulating signal modulated carrier waves, the type of modulation of which Vmay vary during transmission Y due to natural causes, and automaticmeansconnected with said system and energized by energy Y Y therefrom to vary`the ,demodulation characterf isticv of said system,V as thetype of` saidmodulation on said wave varies;Y

2. In combination aV thermionic drevicellfoi` demodulating signal modulated carrier waves,` theY type of modulation of which .may vary during transmission ydue Vto -natural fcauses, signal re= ceiving and amplifyingV means, and 'automatic' means connected withfsaidz deviceand with said .receiving and amplifying means Vand energized by energy from'the latter to vary the demodulation characteristicoi said device as the typeof modulation of saidwave varies. f

3. In fco'mbinationa system for receiving and amplifying signal modulated carrier waves, the j n typel of modulation Yo Whichrmayvaryduring transmission due to natural causes,.thermion1c signal demodulating Vmeans connected at its input to-said system, automatic means connected Ywithgsaid system Vand with'rsaid demodulating Y Vneans energized byV energy from s aidsystem to. YVary the characteristic. of Ysaid demodulating..

means as the typefof'said Waves varies;y and automatic means connected with said system and energized Yby carrier Waves therein to maintain,

saidV device tuned to'said carrier. wave. e Y 4.v In combination, a system for receivingfcare .15T 1 The circuit of Fig. 1 may also be arranged so vrier Waves modulated in amplitude which modulation may be distorted during transmission to simulate phase modulation and automatic means connected with said system andenergized by energy therefrom to alter the character of said system from an amplitude modulated wave receiving system to a phase modulated wave receiving system.

5. In combination, a system for receiving and amplifying carrier waves modulated in amplitude which modulation may be distorted during transmission to simulate phase modulation, Wave demodulating means. connected at its input to the output of said system, and automatic means. connected with said system and With said Wave demodulating means and energized by wave energy from said system to alter the character of said demodulating means from an amplitude modulated Wave demodulating means to a phase modulated Wave demodulating means.

6. In combination a system for receiving carrier Waves modulated in amplitude which modulation may be distorted during transmission to simulate phase modulation, automatic means connected with said systemV andV energized by wave energy therein to alter the character of said system from an amplitude modulated wave receiving system to a phase modulated Wave receiving system, and automatic means coupled to said system and energized by Wave energy therein to maintain said system tuned to the wave being received.

'7. Means adapted to receive a signal carrying carrier Wave, the type of modulations on which may vary from time to time during transmission comprising in combination, a carrier Wave receiver including demodulating means, and means connected with said receiver for varying the de- :modulation characteristic of said demodulating means as the type of modulation of said wave varies.

8. Means adapted to receive a signal carrying carrier Wave, the type of modulation on Which may vary from time to time during transmission comprising in combination, a tunable carrier Wave receiver including demodulating means,

means connected with said receiver and said demodulating means for varying the demodulation characteristic of said demodulating means as the type of modulation of said Wave varies, and means connected with said receiver for varying the tune thereof as the frequency of the received carrier Wave varies.

9. An all purpose receiver comprising in combination signal'receiving and amplifying means of the heterodyne type including a high frequency oscillator, a demodulator and an intermediate frequency amplifier, a filter having its input electrodes coupled With said intermediate frequency amplifier, a pair of thermionic tubes, a circuit connecting the output of said filter in push-pull relation .with like electrodes in said tubes, a circuit connecting the output of said intermediate frequency amplifier in parallel relation with like electrodes in said tubes, a transformer having a primary Winding connected in parallel With the output electrodes of said pair of tubes, a second transformer having a primary Winding connecting the output electrodes of said pair of tubes in phase opposition, a second pair of thermionic tubes one of Which has its control electrode and cathode connected to the secondary Winding rof said first named transformer and the other of which hasits control grid and cathode connected to the secondary Winding of said second named transformer, a pair of demodulator tubes, a circuit connecting the output of said filter in phase opposition to like electrodes in said pair of demodulator tubes, differentialmodulating means ing means, and a circuit connecting the output of said intermediate frequency amplifier in phase to like electrodes in said pair of demodulator tubes.

l0. The method of demodulating signal modulated Wave energy the character of the modulation of which may vary during transmission which includes the steps of, beating said Waves With local oscillationsto produce a signal carrying beat note, stripping all signal modulations from energy of said beat note energy, combining said last named energy with original signal Vcarrying beat note energy in phase quadrature to obtain a component, Acontrolling the frequency of the local oscillations in accordance with said component, combining energy from which all signal modulations have been removed in phasev displaced relation With original signal carrying beat note enerphase of said last energies as combined in accordance With variations in the character of the modulations on said signal carrying beat note.

1l. An all purpose receiver comprising in combination signal receiving and amplifying means of the heterodyne type including a high frequency oscillator, a demodulator and an intermediate frequency amplifier, a filter having its input electrodes coupled with said intermediate frequency amplifier, said filter circuit having an output, a pair of thermionic tubes, a circuit coupling the output of said filter with like electrodes in said tubes, a circuit coupling the output of said intermediate frequency amplifier in parallel relation with like electrodes in said tubes, a first transformer having a primary Winding connected in parallel With the output electrodes of said pair of tubes, a second transformer having a primary Winding connecting the output electrodes of said pair of tubes in push-pull relation, a relay comprising a second pair of thermionic tubesk one of Which has its control electrode and cathode connected to the secondary winding of said rst named transformer and the other of which has its control electrode and cathode connected to the secondary Winding of said second named transformer, a signal coupling tube having a control grid, and a relay including two contacts one of which is connected to the vsecondary Winding of said first transformer and the other of Which is connected to the secondary Winding of said second transformer, said relay also having an armature differentially connected to the control grid of said last named tube.

l2, The method of receiving signal modulated wave energy Vthe character of Vmodulation on which may vary during transmission which irl-- the character of themodulation on Athe Wave' varies.

13. The method of demodulating signal modulated Wave energy the character of themodulation of which may vary during transmission V gy to render the signal and relatively varying the VWhichincludes A'the steps of, stripping lall signal t modulation fromaportion of the wave energy,

combining said'energy from which all signal mod- Qulations have been"stripped vinmeanY phase Adis- -placed relationgwithforiginal signal energy, and relatively varying the mean phase displacementl of saidenergies as combined in ,accordance with variations in the character of theimodulationson said signal carrying 'Waveenergy.Y Y. ,Y Y 14.111 asystemlforreciving Waves modulated in amplitude vor phase and for automaticallyad- Y `justingssaid"system to respond predominantly to i the -particulartype 'oflmodulatio'n on saidwave,

fa Wave-absorbing and amplifying means, said amplifying means having an outputV circuit, Va signal demodul'a'torcomprising-a,pair of ther- [mionic tubes-eachihaving VanA anode, -a Vcathode said circuits,` andan additional me'ans coupling Y saidv outputfcircuit'V to saidaphase modulator forv and a `control grid, 'a circuit coupling said output circuitlinjrpush-pull relation to the control grids L Aand cathodesfof .said-tubes, a circuit 'coupling s aid output circuit in parallel with the control gridsV and cathodes of -Ysaid tubes, ail-iter ingonc `of saidrcircuits, ,aj ,phase 177Vmodulator in one-of Ymodulating the phase' of ltheenergy reaching `said VVdetector-control grids-oversaidlone of saidpaths Vin accordance with the'characterV of the signalA Vin amplitude or phase and for automatically energy lin'said loutput circuit."V

15. "In :a .system lfor receivingY Wavesv modulated I adjusting said system to respond .predominantly to the particular typeof modulation on said Wave, a wave Aabsorbingand amplifying means,

said amplifying means havingan output circuit,`

'apair of thermionic demodulator tubes each having an'anode, acathodeanda control grid, acir- Acuit coupling said output circuit in push-pull Y Y relation Ito thecontrol Vgrids; and cathodes of said i tubes, aV circuit coupling said output 5circuit Vin parallel Withthef'con'trol Vgrids and cathodes of said tubes, a filter vm one fof said circuits, a circuit connected Vwith thefoutput electrodes of V sa'id'def Ymodulator tubes, and vmeans connectedA Withthe control grids ,ofsaid tubes andicontrolle'd by the vcharacter of thermodulation onithe received-Waves i for producingcurrents Yin said output circuit rof said demodulator tubes predominantly characautomatically adjusting said system `to respond ypredominantly to the particular-type of modu-V lationofrsaid Wave-wave absorbing and ampli- V:fying means including a tunable ,circuit,V said means havinganoutput circuit, a signal demodulator device comprisinga :pair ofV thermionic de- Itector tubes each having an anode, a cathode and acontrol grid, a circuit couplingsaid `output cir- Y cuit in push-pull to the control grids and cath- Vodes of saidtubes, av circuit .coupling said voutput circuitlin parallel with the'control grids and'cathodesV of said :tubesja yfilter VVin one of said'last Y named-circuits, a vcircuit connecting the anodes of said tubes in ,push-pull relation, a y'frequency Y i control circuit coupling :the anodesof said'tubes l each-having their controlgrid coupledto the an- Y to saidftunablefcircuit, apair ofcoupling tubes eachi having f anfanode anda control .gi-id and l ode of a different one 'of said'iir'st named tubes,

`4a circuit connecting the anodes of said coupling tubesin parallel, a-circuitcoupling the anodes of Vor the other of saidY output circuits.

said coupling tubes in push-pullrelation, va second t Y pair'of thermi'onic detector tubes each having an` ;anode,'a cathode Aand a control grid, anioutput "circuit connected with the anodes of saidsecon'd Lpairofdetector tubes,'a circuit coupling likeele'c-gi: -trodesvin`isaid second-pair'of'detector,tubes iin i,

phase to said first named output circuit, a circuit connecting like electrodes in; said lsecond,pair-'fof i detectors'inphase opposition tosaid "first named F150 ,i u

output circuit, ltering 4means in vone of Asaid .last

two circuits, yphase modulating meansY in ithefo'th'er l i of said last named' circuits; saidphase modulat- 'ing means comprisinga pair of 'thermionic mod- Y I ulator tubes having their control gri-ds connected in phase opposition by a Vcircuit coupled ,to saidfw first named output circuit and their anodes conzne'ctedlin :parallel by a vcircuit coupled tothe controlgrids of said second pairV ofdetectors; a sec- 'l .ond 'pair of coupling rtubes, each .having an Eanode and a control grid, a circuit coupling `the contr-ol Y gridlofY-one4 of said lastnamed coupling tubes to Y the circuit connecting Ythe anodes Vof `said-'first named'pair of coupling -tubes'in parallel, and .aV

circuit coupling' the vcontrol gridr of the-:other of fsaid last named pair of-coupling tubes lto thefcircuit connecting the-'anodes of said firstnamed f Y'pairof coupling :tubes in push-.pullfrelatiou if' Y `f 17. VIn asystemiforreceiving-Wavesmodulated Y in .amplitude or phase and for automatically l'ad- Y justing `said system tov respond predominantly to 'the particular type `of *modulationY on said `Wave,1a

Vyvaveabsorbing and amplifying means, -saidjamplifyin'g means having anoutput circuit, a signal demodulator comprising a pai-r of'thermionic tubes each having an anode,-a cathode-anda control-grid, a circuit coupling said output circuit in push-pull to thecontrol grids and cathodes of said lpair of tubes, a circuit coupling 'saidoutput circuit-in parallel with the control grids and cathodes of said vpair of tubes, a Aiilter in one o f anodes of said tubes in parallel,anloutputfcircuit f connecting theanodes 'of said tubesin misti-pull Y -relation,`arelay coupled -to said output,` circuits, af coupling tube havingY input electrodes;and",y

'means' cooperating with said relay-and rwith said coupling tube input electrodes-for coupling the input electrodes of said couplingtube -to one 1 8.V In combination, a system ifor'rec demodula'tingV signal modulated carrier Waves, .the '-type'of modulation of VWhich may varyV in tra-nsmissionV dueY to natural causes, and automatic eiving andY a rmeans connected with said system Vfor changing the -demodulation characteristic of said system 'inkl Yaccordance With'varia'tions in the type of modulation of said wave.

19. In combination, a system for der no'dulating,k carrier Waves modulated in phase or amplitude, l

fcc Y thetype ofthe modulation of which may vary in Vtransmission due tonatural causes to resemble amplitude and phaseY modulation respectively,

automatic means connected With said system "for varying the demodulation characteristic Yof said system asthe typeV of said modulation of said` wave varies, and automaticmeans connected with said system for tuning said system vto 'thewaveV toV be received irrespective of variations in the Ymean frequency of said wave. i, i, 1 20. Inr combination, -an electronjdischarge'de'-` modulator device havingV inputand ,outputelectrodes and ha'vingitsV input electrodes energizedV by signal modulated carrierY Waves, the. typeY of Y vvmodulation ofwhich may vary intransmission i due to naturalV causes, and.le1ectron discharge4 '40 said circuits, an output circuit connecting 'the tube means having input electrodes and output electrodes connected with said device and controlled by the character of the modulations of the carrier wave energy in said device for Varying the demodulation characteristic of said device as the type of modulation of said carrier Wave varies.

21. In combination, an electron discharge demodulator system having input and output electrodes and having its input electrodes energized by carrier waves modulated in phase which modulation due to natural causes may be changed during transmission to simulate amplitude moddulation, and means connected with the output electrodes of said demodulator and energized by said modulated wave for automatically varying the demodulation characteristic of said electron discharge demodulator system as the modulation on said Waves changes to simulate amplitude modulation.

22. In combination, a system for demodulating carrier waves modulated in amplitude which modulation due to natural causes may be changed to simulate phase modulation, and means connected with said system for automatically varying the demodulation characteristic of said system as the modulation on said carrier Waves changes to simulate phase modulation.

23. In combination, a tunable circuit for receiving carrier Waves modulated in phase which modulation due to natural causes may be changed to simulate amplitude modulation, a demodulator connected With said circuit, means connected with said circuit and demodulator for automatically varying the demodulation characteristic of said demodulator as the character of modulation on said Wave changes, and means connected with said circuit and said demodulator and energized by Wave energy therein to tune said circuit to the carrier Wave being received irrespective of variations in the frequency thereof,

24. The method ofgreceiving signal modulated wave energy the character of modulation on which may vary during transmission which includes the steps of, ltering said signalling Wave energy to derive therefrom a component from which signal modulations have been substantially removed, combining said filtered component with signal carrying wave energy to demodulate the latter, and varying the mean phase relation of said component and wave energy as combined relative to a substantially phase quadrature relation as the character of the modulation on the Wave varies. 

